Temperature control valves are used to control fluid temperatures in turbines, compressors, and engine jacket water and lubrication oil cooling systems. They are suitable for process control and industrial applications where fluids must be mixed or diverted to achieve optimal temperatures. They may also be applied to cogeneration systems to control temperatures in the heat recovery loop, assuring proper engine cooling and maximizing heat recovery.
Valves used in industrial applications most commonly are defined by the number of ports they have. As the name suggests, a 2-way valve has two ports, a 3-way valve has three ports, and so on. Since different valves support different flow rates, temperature ranges, fluid types, and pressures, knowing these requirements will help you specify the appropriate valve. AMOT manufactures two types of 3-way control valves: thermostatic (internally sensing) and actuated (externally sensing).
Types of Temperature Control Valves
Thermostatic Control Valves
A valve that is actuated by internally sensing and controlling the fluid temperatures is called a thermostatic valve. This type of valve is self-contained without any external power source. AMOT pioneered this technology in 1948 when we introduced into our valve design a special wax that remains in a semi-solid form and is highly sensitive to temperature changes. As the temperature of the fluid changes, it causes the wax to expand or contract which, in turn, slides the valve up or down, opening or closing ports.
3 inch Model BO 2 inch Model BO Model R
The operating temperature range is determined by the chemical composition of the wax material and is preset in the factory according to the engine or equipment manufacturer’s recommendations. Once the thermostatic element is calibrated to a set temperature, it cannot be changed unless a new element is installed. This rugged, yet simple, design prevents operators from accidentally running the equipment too hot or too cold which could lead to higher fuel consumption, costly repairs, and downtime.
Actuated Control Valves
In contrast to internally-sensing valves, an actuated control valve is usually part of a complete system that senses temperature changes using an external probe. The probe sends a signal to a control panel that will open or close the valve ports using an external power source. Typical system types include electric, pneumatic, or a combination of both. Although more components are necessary for this type of valve to work, they do offer several benefits. First, they tend to be much more accurate, so if your application requires very precise temperature control, this may be a better option. Second, unlike thermostatic valves, these systems allow flexible adjustment of the temperature range if operating conditions change.
Electric Model G Valve Pneumatic Model G Valve Temperature Probe PID Controller
How Are They Used?
AMOT’s thermostatic and actuated valves both work equally well for applications that require mixing fluids of two different temperatures or for diverting fluids to a cooler, heat exchanger, or radiator. In addition, AMOT valves can operate in any position, allowing you to mount the valves based on what works best with the existing pipework. The diagrams below show typical piping configurations for each application.
When valves are used for mixing service, Port C is the cold fluid inlet port from the cooler, Port B is the hot by-pass fluid inlet, and Port A the common outlet. Port A is the temperature sensing port and will mix the hot and cold fluids in the correct proportion to produce the desired outlet temperature leaving Port A.
When valves are used for diverting services, the inlet is Port A (temperature sensing port), with Port C being connected to the cooler, and Port B connected to the cooler by-pass line.
If you’re unsure of what valve would work best for your application, our selection guide, product filters, or flow rate calculator can narrow down the options. AMOT also has a knowledgeable customer service team and application engineers to help with nonstandard or complex challenges.